More 3D than 3D: Stereoscopic Defined

Let's start with reality: we live in a world where things occupy a finite volume of space at any given moment in time... Alright, maybe that's not a good way to explain this. Let me try again. Stuff we see in real life has some width, some height and some depth. Our life in our 3D world and our two eyes give us the ability to quickly and easily judge position and dimensions of objects. 3D video games try to approximate this by drawing a two image that has many of the same "depth cues" we use to judge position and shape in reality.

Looking at a picture of something, a 2D image can help us perceive some of the depth that we would have seen if we had stood at the same location as the camera: stuff that's further away appears relatively smaller than the foreground. Shadows and lighting help give us a feel for dimensions as they fall on objects. If we were to talk about video, we would see parallax in effect making it look like objects closer to the viewer move faster than objects further away. Our experience tells us that we can expect certain constants in our reality and we pick up on those and use them to judge things that look similar to reality. Video games exploit all these things to help tell our brains that there is depth in that monitor. Or maybe we're looking at a video of something that was reality. Either way, there is something major (aside from actual depth) missing.

Though we can judge 3 dimensions to a certain extent based on depth cues, having two eyes see objects from two slightly different positions is what really tells our brain that something has depth. The combination of these two slightly different images in our brain delivers tons of information on depth. Trying to play catch with one eye is tough. Just ask your neighborhood pirate.

Seeing two different images with your two different eyes, or rather presenting two different images of the same thing from slightly different positions, is what stereoscopic 3D is. It's right there in the word ... ya know ... stereo ... and scopic. Alright, moving on.

If you've ever tried looking at those "magic eye" pictures, you know what impact just stereoscopic info can have. For those who don't know, a magic eye image is a seemingly random looking pattern that when viewed with your eyes looking "through" the image reveals a hidden 3D picture. Though there is absolutely no other depth information in the picture, no lighting or shadows, no perspective projection, nothing but basic shapes that each eye picks up when you focus through the image, the 3D effect is pronounced and looks "deeper" than any 3D game out there.

This is not a sailboat.

Combining stereoscopic information with all the other depth information makes for a dramatic effect when done properly. Correct rendering and presentation of left and right eye images with proper 3D projection, lighting all that simply looks real enough to touch. Viewing a game properly rendered for stereoscopic effects can range from feeling like looking at a shoe box diorama or a popup book to looking through a window into the next room.

Hollywood tried stereoscopic 3D with anaglyphs (those red and blue images you need the red and blue glasses for), but it didn't really take off except as a sort of lame gimmick. Back in the late 90s and early this century, we saw the computer industry test the waters with active shutter glasses that worked quite a bit better. Rather than displaying a single images with both eye views superimposed requiring filtering, shutter glasses cover one eye while the entire screen displays an image rendered for the other eye. That eye is covered while the first is uncovered to see it's own full resolution full color image. When done right this produces amazing effects.

There are a couple catches though. This process needs to happen super fast and super accurately. Anyone who spent (or spends) hours staring at sub-60Hz CRTs knows that slow flicker can cause problems from eye strain to migraines. So we need at least 60Hz for each eye for a passable experience. We also need to make absolutely certain that one eye doesn't see any of the image intended for the other eye. Thus, when building active shutter glasses, a lot of work needs to go into making both lenses able to turn on and off very fast and very accurately, and we need a display that can deliver 120 frames per second in order to achieve 60 for each eye.

Early shutter glasses and applications could work too slowly delivering the effect with a side of eye strain, and getting really good results required a CRT that could handle 120Hz and glasses that could match pace. It also required an application built for stereoscopic viewing or a sort of wrapper driver that could make the application render two alternating images every frame. Requiring the rendering of an extra image per "frame" required realtime 3D software to be very fast as well. These and other technical limitations helped to keep stereoscopic 3D on the desktop from taking off.

There is still a market today for active shutter glasses and stereoscopic viewing, though there has been sort of a lull between the production of CRTs and the availability of 120Hz LCD panels. And while LCDs that can accept and display a 120Hz signal are just starting to hit the market, it's still a little early for a resurgence of the technology. But for those early adopters out there, NVIDIA hopes to be the option of choice. So what's the big deal about NVIDIA's solution? Let's check it out.

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54 Comments

So how is this different from my ELSA 3d shutter glasses from 1999? The glasses I paid $50 for back then are just as good as this $200 setup in 2009? Great job re-inventing the wheel and charging more for it nVIDIA.

There is a reson shutter glasses didn't catch on. Ghosting being the worst problem, along with compatibility, loss of brightness/color accuracy, performance hits, the need for high refresh rate, etc etc etc.

If you are thinking of buying these, don't. You will use them for a few weeks, then just toss them in a drawer due to lack of game support and super annoying ghosting. Reply

I'm perfectly satisfied with the current refresh rate of LCD-panels (60Hz). However what you forgot is the following: if the 3D glasses open and shut 60 times per second (for a 120Hz Panel) the old flicker of CRTs is effectively back. Therefore raising the refresh rate of the monitor to 240Hz would reduce the per eye flicker to an acceptable 120Hz. Not the monitor itself is the culprit here but the 3D glasses reintroduce flickering like in the old days of CRTs (and they are directly dependent on the refresh rate of the monitor).

Wouldn't a ray traced image work far better for stereoscopic viewing? From what I understand the rasterizing technique used by today's graphics cards uses all kinds of tricks and effects to create the perception of a "real 3D world". That's why the drivers have to be customized for every game.

Ray tracing uses a far simpler algorithm to get good results. Every light ray is calculated separately and every game that uses ray tracing should therefore - in principle - easily be customizable for stereoscopic viewing.

I'm thinking of the announced Intel Larrabee which will maybe offer ray tracing acceleration for games and could therefore be much better suited for stereoscopic viewing.

Not sure if I'm right with these thoughts but it would be interesting to see if games that are already available in a ray tracing version (like Quake 4) could be easily adapted to support stereoscopic viewing and what the result would look like.

Apart from that I also think we would need faster LCD-panels (240Hz) to get non-flickering pictures for each eye.

Check out some of the other initiatives, notably iZ3D, who have offered a free driver for all AMD products and XP support (double check the nVidia support for XP, non-existent much?)

nVidia's idea is too little, too expensive, too late. I have built my own dual-polarized passive rig that works great with $3 glasses, unfortunately nVidia has dropped all support (the last supported card is from the 7 series, so "gaming" isn't really an option.)

Thankfully iZ3D has stepped up to provide drivers, but thanks to nVidia's lack of support I have lost so much money on unsupported 8 series hardware that I haven't looked at a game in a couple years.

nVidia has killed my will to game. Dropping support of 3D is not the way to sell 3D (do some research, nvidia has dropped XP, supports only vista, and not even any of the cool displays you can cobble together yourself for less than the $200 this stupid package costs.)